What's the difference between "accelerating T 1", iwatch and mi band?

At present, most bracelets on the market have the functions of step counting, sleep monitoring, heart rate detection, call reminder and so on. You can choose according to your own needs and try to choose some well-known brands. In addition, mi band has many other functions, such as heart rate monitoring, screen unlocking, confidential payment and so on. The total shipment of mi band has exceeded 3000w W w.